“Advancements in track forecasts are making it possible for forecasters to provide greater lead time,” the hurricane center said today in a release.

“With increases in population and infrastructure along vulnerable U.S. coastlines,” Hurricane center director Bill Read said in the statement, “emergency managers need more lead time in order to make life-saving decisions regarding evacuations.”

Read

Starting with the 2010 season, for both tropical storm and hurricanes, watches will be issued when conditions are possible along the coast within 48 hours, and warnings when conditions are expected within 36 hours.

Hurricane watches and warnings will reflect when meteorologists believe winds from an approaching storm will reach tropical storm strength, at 39 mph.

The new timing is a two-edged sword.

Storms can move away at the last minute, causing a lot of unnecessary expense and hassle.

In 1999, in one of the largest peacetime evacuations in U.S. history, 3.5 million people fled the southeast U.S. coast, about 2 million of them in Florida, in advance of Hurricane Floyd. But it stayed off shore and eventually struck the Carolinas. A drive from Jacksonville to Tallahassee that should have taken 2 1/2 hours took up to 10 hours. Studies later showed many evacuated who shouldn’t have, while many stayed who should have left.

But the opposite can be far more perilous.

In 2004, Hurricane Charley appeared to be on a beeline for Tampa Bay but made a slight jog en route that brought it over land in Charlotte County, catching some residents off guard and unprepared.